PS2 games on PS3 store with GS and EE emulated. How is it possible?

These games can be played on PS3's that have no PS2 hardware at all. Does anyone know how it was done? Are 4-5 SPE's slaved to do GS work in an SLI manner? How can the main core handle emulating the memory controllers, VPU, DMA, timings, whatever else there is, or are there specific SPE's assigned to these tasks?

I really want to know some details because a couple of years ago I asked about the possibility of PS3 emulating the PS2 (on this forum), and interesting and different opinions were given. I am still not qualified for very technical descriptions but I tried hard to make sense of what everyone was saying and I just want to revisit this topic since sony has proven to me that PS3's can play PS2 games without having the right hardware.

It is possible they recompiled and rejigged the games a bit to no longer need the specific hardware.

If you still have the source/toolchain then even doing a very 'simple' replacement can vastly outperform something trying to do full emulation because of the significant increase in performance. If you were depending on some 'special' hardware hack that doesn't actually emulate well then you might find that just doing it anentirely different way is plenty fast enough now.

As an example people like to rave about the really cleaver Quake3 inverse square root hack. But modern FPU hardware smokes that now, you really are better just letting the compiler do what it wants. you might find that some things where there is hand rolled assembly, plus the original C/C++ source code it replaced, you can just restore the source code part and it will be just fine.

It can be further helped by someone supplying a library that deals with providing API calls that don't exist on the PS3, but which can be translated more easily into the equivalents with the increased context, rather than trying to patch out such things on the fly.

The cost of doing this will vary massively on a per game basis of course. I have no idea if that is what they did.

Edit: this is basically what [quote=http://arstechnica.com/civis/viewtopic.php?p=21625841#p21625841]Blacken was saying[/url] with "I'm reasonably sure--though I can't prove it--that you'd see better results by re-targeting the code for the RSX."

I took that to be the OP's implication from their last post (based on Blacken's statement that they were not doing additional emulation on the recently released ports to the PS3) and I was refuting it on that basis.

Or he was citing an article that didn't know what it was talking about. Anyone ever think that they'd want a PS3-familiar engineer because their developer-facing toolchain hasn't changed much for the PS4?

(The PS2->PS3 compat library I referred to before is freely downloadable on Sony's moral equivalent of the MSDN.)